When recording synths you sometimes want some room ambiance/live amp sound on the keys. Especially when recording a band live this helps to bring a more realistic picture. Unfortunately, most keyboard amps do not deliver the full range of a keyboards sound or even close to it. You end up with a muted high and insufficient low end. One way I have found to remedy this, is to use studio monitors as the keyboard amp. Even the cheapest of studio monitors deliver a much more pleasing result than the high end expensive keyboard amps. Even a nice home stereo will do the trick, anything so that you never have to record another one of those Roland cube keyboard amps!

As someone who not only plays keyboards but also writes my own sounds, this is a total no brainer.
Just about all Synthesizers are capable of producing the full range of audible frequencies so it only takes a little bit of thought to realise that you need a system that can reproduce that full range otherwise you just can’t hear what you are really playing.
It’s even more important if you are writing your own sounds, especially if you are then recording those sounds via a direct line connection to your recording system.
Back in my early days of being a keyboard player, I bought a pair of PA speakers + amp to go with my keyboard. I was ignorantly happy with that set-up for quite some time, but that I have a proper pair of studio monitors I have graduated to a whole new level of sound quality that makes my previous efforts totally laughable.